Using the illumination of miniature light bulb series to achieve a decorate effect has been known. However, to dispose light bulb series in a predetermined pattern, the prior art means adopted a support post (2) to receive light bulb holders (3). As shown in FIG. 1, the combination of a light bulb holder (3) with a support post (2) according to the prior art structure is obtained by means of extending two hook-like arms (11) and (12) of an annular retaining element (1) into an opening (21) formed on the support post (2). When those light bulbs are lit up, a preset image or pattern appears. The shortcoming adhered to such an arrangement is an insufficient bonding strength between the annular retaining element (1) and the light bulb holder (3). Thus it often happened that light bulb series got out of position. Furthermore, the connection wires of light bulb series often scattered over a large area without any fixing, which is detrimental to the decorative effect and may bring an unpleasant accident.
In view of the above problems, the primary object of the invention is to provide a coupling mechanism in which the shortcomings in a conventional structure are eliminated and that can enhance the decorative illumination effect of miniature light bulbs by means of integrated planar arrangements including light bulbs and electrical wires. Now the features and advantages of the invention will be described in more detail with reference to the accompanying drawings.